enum MusicMode{
  // 单曲循环
  singleLoop,
  // 顺序播放
  sequentialPlay,
  // 随机播放
  randomPlay;

  MusicMode getNextMode() {
    MusicMode currentMode = this;
    int nextIndex = (currentMode.index + 1) % MusicMode.values.length;
    return MusicMode.values[nextIndex];
  }
}